1. Technical Field
The present invention relates to defect inspection systems for the semiconductor industry. More particularly, the present invention relates to an automated defect inspection system for wafers or other semiconductor or electronic substrates of any kind or type that are transparent, opaque or otherwise capable of allowing at least some visible light to pass through.
2. Background Information
Over the past several decades, the semiconductor has exponentially grown in use and popularity. The semiconductor has in effect revolutionized society by introducing computers, electronic advances, and generally revolutionizing many previously difficult, expensive and/or time consuming mechanical processes into simplistic and quick electronic processes. This boom in semiconductors has been fueled by an insatiable desire by business and individuals for computers and electronics, and more particularly, faster, more advanced computers and electronics whether it be on an assembly line, on test equipment in a lab, on the personal computer at one's desk, or in the home electronics and toys.
The manufacturers of semiconductors have made vast improvements in end product quality, speed and performance as well as in manufacturing process quality, speed and performance. However, there continues to be demand for faster, more reliable and higher performing semiconductors.
One process that has evolved over the past decade or so is the semiconductor inspection process. The merit in inspecting semiconductors throughout the manufacturing process is obvious in that bad wafers may be removed at the various steps rather than processed to completion only to find out a defect exists either by end inspection or by failure during use.
Certain wafers are transparent, translucent, opaque or otherwise capable of transmitting light therethrough. Also, some silicon (not transparent or opaque) have through holes or mask properties that allow visible light to be transmitted through certain portions. These wafers that are transparent or opaque are generally made of type III-V or II-VI compounds and include gallium arsenide, indium phosphide, silicon carbide, and other non-silicon based substrates. These wafers may also be glass or oxide based which includes quartz and fused silica compounds.
Often these transparent or opaque wafers contain features on the back side (the side against the plate or stage) or inside the wafer that it is desirable to inspect. In some scenarios, brightfield or darkfield illumination as is disclosed below in the incorporated by reference August Technology patent applications, is sufficient to illuminate the wafers for inspection even where the features are on the backside or inside. However, in certain wafers, backside illumination is desirable or necessary to better illuminate the features to be inspected.
It is this need that the present invention addresses.